1. Field of the Invention
The present invention relates to a multi-wavelength semiconductor laser device that emits different wavelength light beams.
2. Description of the Prior Art
An optical disc such as a compact disc (CD), a digital versatile disc (DVD), and a “Blu-ray Disc”™ (BD) has been increasingly used now as large capacity storage media. Laser diodes used for reading/writing from/to these discs have respective different emission wavelengths: a CD laser diode has an emission wavelength of 780 nm band (infrared), a DVD laser diode has an emission wavelength of 650 nm band (red), and a BD laser diode has an emission wavelength of 405 nm band (blue-violet). Hence, in order to treat data for a CD, a DVD, and a BD in a single optical disc drive, required are three light sources of infrared, red, and blue-violet.
There has been a conventional multi-wavelength semiconductor laser device in which a red laser diode and an infrared laser diode are arranged in parallel and bonded on a blue-violet laser diode mounted on a heat sink, to be able to treat data for a CD, DVD, and BD in a single optical disc drive (see, for example, JP 2006-59471A (FIG. 4)). There has also been a multi laser diode array that is configured by mounting a plurality of laser diodes on a bendable submount plate and then bending the submount plate in a triangular prism shape so that the mounted laser diodes are arranged inside thereof, to thereby position the light sources of the laser diodes close to each other (see, for example, JP 08-111562A (FIG. 2)).
In the multi-wavelength semiconductor laser device disclosed in JP 2006-59471A, however, since the infrared and the red laser diodes are arranged and bonded on the blue-violet laser diode, there has been a problem in that heat generated during operation of the infrared and the red laser diodes cannot be efficiently dissipated to the heat sink. Moreover, the emission points of the infrared, the red, and the blue-violet laser diodes are difficult to be positioned at the same distance from the center of the laser device package, resulting in a problem of complicating their optical design.
In the laser diode array disclosed in JP 08-111562A, on the other hand, the respective emission points of the laser diodes can be positioned at the same distance from the center of the laser device package. However, since the laser diodes are arranged on the inside of the submount plate bent in the triangular prism shape, there has been problems of complicating wiring to the laser diodes and requiring longer time in the wiring process.